Field of the Invention
The present invention relates to an imaging apparatus. More particularly, the present invention relates to a technique capable of tracking an imaging target in a continuous shooting operation.
Description of the Related Art
A continuous shooting includes a plurality of photographing operations successively performed. A technique capable of driving a lens while predicting the movement of a moving imaging target in such a continuous shooting is conventionally known. For example, the method discussed in Japanese Patent Application Laid-Open No. 8-75999 includes storing a plurality of previously acquired focal point detection results, selecting an optimum mathematical function that predicts a future image surface position of an imaging target, and continuously adjusting the focus on an imaging target (namely, tracking the imaging target) by driving a focusing lens according to the selected mathematical function. The tracking can be defined as an operation for driving the focusing lens in such a way as to adjust the focus on a moving imaging target.
The method discussed in Japanese Patent Application Laid-Open No. 8-75999 does not include any lens driving performed after completing a photographing operation and before starting the next focal point detection. If the imaging target is a moving object, a moving distance of the imaging target during a time interval between the photographing operation and the next focal point detection will not be negligible. In this case, if the moving speed of the imaging target is higher, the imaging target image surface position will greatly change during the time interval between the photographing operation and the next focal point detection although it depends on the position or moving direction of the imaging target, compared to a case where the speed is lower. In the continuous shooting, it is required to drive the focusing lens in a limited time (i.e., during the time interval between the focal point detection and the photographing operation). Therefore, if the imaging target image surface position changes greatly, it may be difficult to sufficiently drive the focusing lens by a required drive amount calculated based on a focal point detection result.
In view of the foregoing, prior to the driving of the focusing lens after completing the next focal point detection, a lens driving is performed preliminarily based on a previously acquired focal point detection result after completing the photographing operation and before starting the next focal point detection. In this case, it becomes feasible to improve the imaging target tracking accuracy by the driving of the focusing lens performed after completing the focal point detection and before starting the photographing operation.
When the driving of the focusing lens is performed before starting the next focal point detection as mentioned above, a significant time has already passed since the previous focal point detection. If the focal point detection timing deviates greatly from the timing for driving the focusing lens based on the focal point detection result, there will be a great difference between an imaging target position at the focal point detection timing and an imaging target position at the focusing lens driving timing. Accordingly, the imaging target tracking accuracy may deteriorate if the previously acquired focal point detection result is used.